The purpose of this research project is to develop a method for the purification of urinary erythropoietin which does not rely on differences in size and charge between erythropoietin and other proteins in human urine. To this end, we have employed affinity chromatography using lectins and other ligands immobilized on beaded agarose. Recently we have identified a carbohydrate residue on erythropoietin which s bound by certain lectins which do not bind to the bulk of the urine proteins. Having identified this carbohydrate residue, we can now employ other lectins which selectively bind this carbohydrate and no other in contrast to the lectins we are currently using. Four such lectins which are highly specific with respect to affinity for the carbohydrate of interest are known. We have purified two of these almost to homogeneity by a simple rapid technique with retention of their carbohydrae binding activity. We plan now to determine if these two lectins can reversibly bind erythropoietin and if so, whether they can be used in separating the hormone from other proteins in the urine.